1. Field of the Invention
This invention relates generally to electronic combination locks for security doors and the like. In particular, this invention relates to an electronic lockout circuit which prevents a radio frequency signal from falsely activating an electronic combination lock and thereby opening a security door.
2. Description of the Prior Art
Electronic combination locks and electronic locking systems are used on security doors to prevent unauthorized access through the doorway. An electronic lock system generally includes a code entry switch module mounted with the module's switches accessible from a nonsecured area, an electrically activated door strike mounted in a security door frame, and an electronic control unit mounted in a controlled space and which monitors the code entry switches and activates the door strike when a user specific combination is provided through the code entry switches.
Under normal circumstances these prior art electronic combination locks and electronic locking systems function effectively in allowing only authorized persons with an assigned access code to gain entry into a secured area. However, where there is radio transmitter equipment in the vicinity of an electronic combination lock, the electronic control unit may respond to the radio frequency signals generated by the transmitter and provides an electrical signal to the door strike activating the door strike which opens the security door, thereby allowing unauthorized access to the secured area.
With this and other disadvantages known to prior art electronic combination locks the present invention was conceived and one of its objects is to provide an electronics circuit which may be used to prevent radio frequency signals from falsely unlocking security doors that have electronic locking systems.
It is another object of the invention to provide an electronics circuit which may be easily adapted to conventional as well as state of the art electronic combination locks to prevent the accidental opening of a security door by a radio frequency transmitter.
It is still another object of the invention to provide a relatively simple and inexpensive electronics circuit which prevents the accidental activation of an electronic combination lock by a radio frequency transmitter.
Various other advantages and objects of the present invention will become apparent to those skilled in the art as a more detailed description of the invention is set forth below.